Exponential growth is exhibited when the rate of change—the change per instant or unit of time—of the value of a mathematical function is proportional to the function’s current value, resulting in its value at any time being an exponential function of time, i.e., a function in which the time value is the exponent. Exponential decay occurs in the same way when the growth rate is negative. In the case of a discrete domain of definition with equal intervals, it is also called geometric growth or geometric decay, the function values forming a geometric progression. In either exponential growth or exponential decay, the ratio of the rate of change of the quantity to its current size remains constant over time. — Wikipedia

Juul annual sales projected to top $3 billion after profitable... ReutersE-cigarette maker Juul Labs Inc's revenue is expected to triple this year to about $3.4 billion following a profitable 2018, Bloomberg reported on Friday. […]